For a big project I need a strong and slow engine. As I gathered it is common get a used windshield wiper motor. I got a used one from my neighbor who fixes cars but the motor turned out to be something strange, not like any other wiper motor I can find on the internet (doesn't look like them either). I experimented with it to understand it. If I remember it has 5 connections and I guess two are for this auto-parking feature but I'm not interested in that. Leaves three connections and now to bizarre(to me).Let me call them c1, c2 and c3. The possible connections that can be made with a power source (plus and minus) is listed here and what happens:+c1 -c2 motor rotates one direction.-c1 +c2 motor rotates the same direction (even though I reversed polarity).+c3 -c2 motor turn the other direction.-c3 +c2 motor turns the other direction (again, I reversed polarity and it spins the same, but at a different speed).+c1 -c3 short circuits-c1 +c3 short circuits

The thing about different speed I guess is for the different speeds of the wipers.And the c2 should be the "ground", because it would be in touch with the rest of the metal of the car it was mounted in at the beginning.

I understood that I needed to control high currents with the arduino, but I didn't want a mechanical relay (the direction might be changing quite often, perhaps a few times per second). I bought a Parallax HB-25 Motor Controller (bought it in fact before my strange wiper motor).

You might see the problem here, to control direction of a motor the HB-25 changes polarity of its output ports (M1 and M2). That wouldn't help me.And now I'm getting out into the more deep waters, for me at least. I think that adding a few diodes might solve my problem.

I attach my suggestion. I hope people can tell me if this will do what I want. When the HB-25 puts positive on M1 and negative on M2 the motor rotates one way and when changing polarity of M1 and M2 it rotates the other way.Second, I need help with selecting the diodes. I plan to buy from conrad.com, they have a big selection of diodes. Is a "standard" diode okay? Or a Schottky diode? What I've tried to read other diodes aren't of interest here.So... the voltage I guess will be around 13-14VDC and the motor might get stalled (high current draw). I don't know anything about the motor's power. But looking around there seems to be wiper engines in the range of 50-150 watt. So if buy diodes that are good for up to 15A, which should I buy? Or if the price would be the close for 25A I would take that (25A is the max continuous for the motor controller).

I have seen that video but that isn't similar to mine, neither wiring or look. As seen the output shaft of the typical motor in the video is at a right angle to the axle of the DC motor inside it. My motor has the output shaft (after reduction gears) parallel to the DC motor axle. I don't have it here so I can't take a picture of it, sorry.

The neighbor had pulled it out of some car at the scrap yard. He don't remember which car. There are no markings or name at all on it of what I remember (the motor is at my parents house, can't check).But I did sit and test all the ports on it, had connected a ATX PSU modded for such task.I tried to pry it open but I couldn't. It is something internally that makes it behave as it do. As far as I know all DC motors change direction when the polarity is changed, or this is some kind of strange engine that won't do that.

Just to clarify, it is not that kind of small motor that connects directly to a wiper via a shaft (used in old tractors and trucks), which also has automatic reversal at the end zones.On my motor it is a little gear, no long shaft out of it. The linkage to a standard wiper blade setup would be connected to this gear.

But given the characteristics of it what I wrote in the first post, would the diode setup work?

But given the characteristics of it what I wrote in the first post, would the diode setup work?

Your diode steering circuit looks like it would work to me. I would use diodes with as high a current rating as you can find (and afford of course). As a second level safety item I would consider adding one automotive style fuse on the single common - lead feeding the motor. Who knows what the stall current would be if the motor was to jam or whatever and while the motor driver seems to have some fuse protection I would consider this second one maybe sized closer (but still more) to what the motor actually draws in your application. Note that because of the voltage drop (across two diodes) there is likely going to be a little 'dead band' around the neutral control speed setting being sent to the controller, but you can probably deal with that in your software if it becomes as issue in your control algorithm.

I remembered I had an arduino with breadboard... I tested the wiring and instead of the motor I had 1 LED+resistor going from "motor 1st +" to "-" in the wiring diagram, and another LED+resistor going from "motor 2nd+" to "-". And then to be sure I switched the LEDs' legs and as expected it didn't shine then but when switching positive and negative input the breadboard the first LED went dark and the other one lit up.

I'm going to buy a car fuse assortment box for mini ATC fuses (small flat car fuses), that is the type that the motor controller has. Because I agree that 25A is probably to much. 10A or 15A will be better. You wrote "single common - lead feeding the motor". Do you mean I anyway should have an extra fuse after the motor (the "-" connector of the motor) or do I get away from this by changing the fuse on the controller.

Window motors have gears on them wiper motors don't have any that you can see.

I didn't know how those looked like so I googled it. Well the principle looks the same as the wiper motor. It has a worm gear reduction. The gears aren't similar either, mine has a lot more teeth, I think is made to be connected to some component with inner teeth (like putting a drive shaft on it or so).I started considering the possibility that it might like some vital components. But a wiper motor has a worm gear that slows it down a lot. This output gear already only turns like 100 rpm (i.e. a few revolutions per second unloaded) which could be suitable for a wiper motor.

To put an end to figuring this out I will ask my mom if she can try to take a few photos of this and send it over (I live far away) to me so I can display it to you guys. But I will make my online purchase tonight (CET timezone) because that webshop has come up with the idea to import the "black friday" phenomena here, so they have a general discount for all purchases.

Well I already have the Parallax HB-25 motor controller (HB = H-Bridge) so I don't need any of those I think.

Here are the pictures. The bend part of the mounting bracket is pointed away from the motor when mounted onto it.And the white cable around the output gear was only for me to visually estimate the rpm when testing.

I found this diode, what do you all think?http://www.produktinfo.conrad.com/datenblaetter/150000-174999/160744-da-01-en-SCHOTTKY_DIODE_DSS25_0025B_TO_220_AC.pdf(no, I won't forgetting cooling of it)

Measure the resistance of the motor windings with a multimeter and divide that into the supply voltage you will be using to get the stall current (Ohm's law). If it's less than 25A then that diode will be fine, with appropriate heatsinking if necessary. If it's a lot less than 25A, then a regular silicon power diode will be suitable and cost less. The only advantage of a Schottky diode in this application is that is has a lower voltage drop, so it dissipates less power and may not need quite as much cooling.

Formal verification of safety-critical software, software development, and electronic design and prototyping. See http://www.eschertech.com. Please do not ask for unpaid help via PM, use the forum.